Fiber optic assembly with both push and pull material

ABSTRACT

The specification relates to a fiber optic cable assembly. The fiber optic cable assembly includes: an outer jacket, the outer jacket being made from polyethylene; a pull material, the pull material being made from aramid and water blocking fibers; a push body, the push body being made from a rigid material so that the fiber optic cable assembly can be pushed without bending; and at least one fiber optic fiber.

BACKGROUND

The disclosed technology relates generally to a fiber optic assembly.

Traditionally, fiber optic assemblies include optical fibers thatconduct light for transmitting voice, video and/or data. Theconstruction of fiber optic cables preserves optical performance of thefibers when deployed in an intended environment while also meetingofficial standards for the environment. For instance, indoor cables forriser and/or plenum spaces may require certain flame-retardant ratingsto meet the demands of the space. These flame-retardant ratings can bein addition to mechanical requirements or desired characteristics forthe space, e.g., crush performance, permissible bend radii, temperatureperformance, and the like. These characteristics are desired to inhibitundesirable optical attenuation or impaired performance duringinstallation and/or operation within the space.

By way of example, some indoor applications use a fiber optic cabledisposed within an armor layer for providing improved crush performancein riser and/or plenum spaces. For instance, conventional armoredconstructions have a fiber optic cable disposed within a metallicinterlocking armor. This interlocking armor can be wound about the fiberoptic cable so that the edges of the adjacent wraps of armormechanically interlock forming an interlocked armor layer with a largebend radius, e.g., greater than 75 mm and a large outside diameter (OD),e.g., 12.5 mm.

SUMMARY

This specification describes technologies relating to a fiber opticassembly with a push body that allows small flexible fiber optic cableassemblies to be pushed through small cable runs, e.g., data centers,cable trays and under raised floors.

In one implementation, a fiber optic cable assembly comprising: an outerjacket, the outer jacket being made from polyethylene; a pull material,the pull material being made from aramid and water blocking fibers; apush body, the push body being made from a rigid material so that thefiber optic cable assembly can be pushed during installation; and atleast one fiber optic fiber.

In some implementations, the push body can be at least one rigid wire.In some implementations, the at least one rigid wire can be made fromsteel. In some implementations, the at least one rigid wire can have adiameter of 0.2 to 0.6 mm. In some implementations, the at least onerigid wire can be partially attached to an inside wall of the outerlayer.

In some implementations, the fiber optic cable assembly can furthercomprise an armor body. In some implementations, the armor body can besteel micro armor.

In some implementations, the pull material can be sandwiched between theouter layer and the armor body. In some implementations, the at leastone fiber optic fiber can be a tight buffer fiber.

In some implementations, the push body can be a rigid, hollow tube. Insome implementations, the tube can be seamless. In some implementations,the tube can be made from stainless steel. In some implementations, thetube can be made from SUS 304. In some implementations, the tube canhave an outer diameter of 0.8 to 2.2 mm. In some implementations, thetube can have an inner diameter of 0.6 to 1.2 mm. In someimplementations, the tube can have thickness of 0.1 to 0.3 mm.

In some implementations, the fiber optic cable assembly can furthercomprise an armor body. In some implementations, the armor body can besteel tube. In some implementations, the pull material can be sandwichedbetween the outer layer and the armor body.

In some implementations, the fiber optic cable assembly can furthercomprise a strengthening material surrounding the at least one fiberoptic fiber underneath the push body. In some implementations, thestrengthening material can be made from aramid and water blockingfibers. In some implementations, the pull material can be made fromaramid and water blocking fibers.

The advantages of the fiber optic cable is that it is highly flexibleand thin but capable of maintaining rigidity for longer runs whenrunning cable thereby making the cable much easier to install and savingspace in data centers, cable trays and under raised floors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side view of a fiber optic assembly of the disclosedtechnology;

FIG. 2 shows a cross section of the fiber optic assembly according toFIG. 1; and

FIG. 3 shows a side view of a second implementation of a fiber opticassembly of the disclosed technology.

DETAILED DESCRIPTION

This specification describes technologies relating to fiber optic cableassemblies. The fiber optic cable of the disclosed technology is small,flexible and armored fiber optic cable with a push body that allows thesmall, flexible and armored fiber optic cable assemblies to be pushedthrough small cable runs, e.g., data centers, cable trays and underraised floors.

Fiber optic cable assemblies refer to the complete assembly of fibers,e.g., buffer tubes, ripcords, stiffeners, strengthening material, outerand inner protective coverings, etc. Fiber optic cable assembliesprovide protection for the optical fiber or fibers within theenvironment in which the cable is installed. Fiber optic cableassemblies come in many different types, depending on the number offibers and how and where it will be installed.

A function of the cable assembly is to protect the fibers from theenvironment encountered in and after installation, e.g., will the cable:(1) become wet or moist; (2) have to withstand high pulling tension forinstallation in conduit or continual tension as in aerial installations;(3) have to be flame-retardant; (4) be installed around tight bends; (5)be exposed to chemicals; (6) have to withstand a wide temperature range;(7) be gnawed on by rodents; and (8) be exposed to any otherenvironmental issues.

The bend radius is of particular importance in the handling of fiberoptic cables. The minimum bending radius varies with different cabledesigns. That is, optical fiber is sensitive to stress, particularlybending. When stressed by bending, light in the outer part of the coreis no longer guided in the core of the fiber so some is lost, coupledfrom the core into the cladding, creating a higher loss in the stressedsection of the fiber. Fiber coatings and cables are designed to preventas much bending loss as possible, but its part of the nature of thefiber design. Bending losses are a function of the fiber type (e.g.,single mode or multi mode), fiber design (e.g., core diameter andnumerical aperture), transmission wavelength (e.g., longer wavelengthsare more sensitive to stress) and cable design (e.g., fire resistanceand/or crush resistance). The normal recommendation for fiber opticcable bend radius is the minimum bend radius under tension duringpulling is 20 times the diameter of the cable. When not under tension,the minimum recommended long term bend radius is 10 times the cablediameter. Besides mechanical destruction, excessive bending offiber-optic cables can cause microbending and macrobending losses.Microbending causes light attenuation induced by deformation of thefiber while macrobending loss refers to losses induced in bends aroundmandrels or corners in installations.

To avoid microbending and macrobending issues, bend insensitive fiberhave been developed. Bend insensitive (BI) fiber cable offers greaterflexibility in demanding environments than traditional fiber cable. Itis typically used in data centers or any space constrained area wheretight bends and flexibility are required. Bend-insensitive fibers mayadd a layer of glass around the core of the fiber which has a lowerindex of refraction that literally “reflects” weakly guided modes backinto the core when stress normally causes them to be coupled into thecladding. In some fibers, a trench, or moat, surrounds the core in bothBI single mode fiber (SMF) and BI multi mode fiber (MMF) to reflect lostlight back into the core. The trench is an annular ring of lower indexglass surrounding the core with very carefully designed geometry tomaximize the effect. Bend-insensitive fiber has obvious advantages. Inpatch panels, it does not suffer from bending losses where the cablesare tightly bent around the racks. In buildings, it allows fiber to berun inside molding around the ceiling or floor and around doors orwindows without inducing high losses. It's also guards against problemscaused by careless installation.

Many applications for BI SMF are in premises installations likeapartment buildings or for patchcords, where it simplifies installationand use. BI SMF is also used in outside plant cables since it allowsfabrication of smaller, lighter high fiber count cables.

In many applications were BI fiber are used, the fiber may be exposedcrush loads as well as rodents. The problem that arises is that thearmor used to protect standard fiber has a bend radius of usually <75and an OD of 12.5 mm. When used in applications with tight bend area,the armored cable either does not fit into tight spaces due to its largeOD and/or does not conform to a necessary bend. In these cases,unarmored fiber optic cables are used. This leaves open the possibilityof the cable being crushed or cut.

Another problem with fiber is that some fiber assemblies does not haverigidity for pushing a cable assembly through a long run. That is, theproper method of pulling fiber optic cables is always to attach a pullrope, wire or tape to the pull material. In these installations, fishtape can be utilized to extend from one side of a long run to the other.Once ran, the fiber assembly can be attached to the fish tape and pulledto the desired location. Using fish tape has its own set of problems,e.g., the attachment gets undone in the middle of the run and needs tobe further secured. Also, there is cost of buying the fish tape andhaving a proper length for your installation project.

The subject matter of the disclosed technology overcomes this problem byincorporating a rigid material within the fiber optic assembly so thatthe assembly can be pushed from one end of a run to the other withoutthe need for fish tape.

As shown in FIGS. 1 and 2, the fiber optic cable assembly 10 can includean outer jacket 12, a pull material 14, stainless steel armor 16, a pushbody 18, strength material 20 and one or more optic fibers 22 a, 22 b.

The outer jacket 12 is the outermost layer of protection for the fibers22 a, 22 b that is chosen to withstand the environment in which thecable assembly 10 is installed. For outside cables, the outer jacket 12will generally be black polyethylene (PE) which resists moisture andsunlight exposure. For indoor cables, the outer jacket 12 may be aflame-retardant jacket that can be color-coded to identify the fibers 22a, 22 b inside the cable assembly 10, e.g., PVC, LSZH, TPU, ETFE orOFNP. The outer jacket 12 thickness can be approximately 0.25 mm-7.5 mmand come in a variety of colors, e.g., yellow, orange, aqua, blue, etc.

Under the outer jacket 12 is the outer pull material 14. The outer pullmaterial 14 can be aramid fibers and a water backing material. The outerpull material 14 can absorb the tension needed to pull the cableassembly 10 during installation. Aramid fibers are used because of theirstrength and the fact that they do not stretch. If pulled hard, thearamid fibers will not stretch but may eventually break when tensionexceeds their limits. For short term stresses, the maximum tension isapproximately 800N. For long term stresses, the maximum tension isapproximately 600N.

The armor 16 can be a non-interlocking stainless steel tube, e.g. SUS204. The benefit of using a non-interlocking armor is that the bendradius is substantially smaller than a bend radius of an interlockedsteel tube. It is also much lighter and easier to work with. The armor16 can be a spiral tube having a gap 17 between each spiraling ring, thegap 17 can be 0.05 mm to 1 mm. The armor 16 cab be a spiral tube havingan outer diameter of approximately 1.5 mm-5.5 mm, a thickness ofapproximately 0.25 mm-0.75 mm and an inner diameter of approximately0.75 mm-5.25 mm. The armor has a crush resistance of approximately a≥100 KGf/100 mm. The armor 14 offers increased crush protection, higheraxial strength and corrosion resistance. However, other armored steeltubes are contemplated.

The strengthening material 20 at least partially surrounds the opticalfibers 22 a, 22 b. The strengthening material 20 may be formed of anysuitable material. According to some embodiments, the strengtheningmaterial 18 can be aramid fibers. Other suitable materials may includefiberglass or polyester. The strengthening material 20 can be aramidfibers which can absorb the tension needed to pull the inner cable andprovide cushioning for the fibers 22 a, 22 b, thus ensuring that theoptical fibers do not stretch or bind within the cable.

Optical fibers 22 a, 22 b can be a tight buffer fiber having a core 62and a cladding layer 64. The core 62 can be a bare optical fiber and thecladding layer 64 can be a nylon both of which can be selected for totalinternal reflection due to the difference in the refractive indexbetween the two. The bare fiber 62 can also be coated with a layer ofacrylate polymer or polyimide. This coating protects the bare fiber 62from damage but does not contribute to its optical waveguide properties.Individual coated fibers (or fibers formed into ribbons or bundles) thenhave a tough resin buffer layer and/or core tube(s) extruded around themto form the cable core. A standard fiber has a primary buffer coating ofapproximately 250 microns and can add a tight buffer coating such as asoft protective coating applied directly to the 250 micron coated fiberto provide additional protection for the fiber, allowing easier handlingand even direct termination for the fiber. In some implementations, theoptical fibers 22 a, 22 b can be 62.5/125 μm multimode fibers, 50/125 μm10G OM3/OM4 fibers, 9/125 μm single mode G.652.D fibers, 9/125 μm singlemode bend-insensitive fibers, or any suitable fibers, for example,G.657.A1, G.657.A2, G.657.B1, G.657.B2, G.657.B3.

The push body 18 can be a seamless stainless steel tube that surroundsthe strengthening material 18 and the optical fibers 22 a, 22 b. Thepush body 18 is capable of acting as a fish tape but can be bent toaccommodate tight turns. In some implementations, the push body can be arigid, hollow tube. In some implementations, the tube can be seamless.In some implementations, the tube can be made from stainless steel. Insome implementations, the tube can be made from SUS 304. In someimplementations, the tube can have an outer diameter of 0.8 to 2.2 mm,an inner diameter of 0.6 to 1.2 mm and a thickness of 0.1 to 0.3 mm.

The fiber optic cable assembly 10 can have (1) a short term maximumtension of 200N and a long term maximum tension of 400N, (2) a shortterm crush resistance (N/100m) of 5000N and a long term crush resistance(N/100m) of 2500N, (3) an insertion loss of 1310 nm-1550 nm and (4) aminimum bend radius of 20D for dynamic and 10D for static.

As shown in FIG. 3, the fiber optic cable assembly 50 can include anouter jacket 52, one or more push bodies 54 a, 54 b, a pull material 56,stainless steel armor 58, and one or more tight buffer fibers 60 a, 60b.

The outer jacket 52 is the outermost layer of protection for the fibers60 a, 60 b that is chosen to withstand the environment in which thecable assembly 50 is installed. For outside cables, the outer jacket 52will generally be black polyethylene (PE) which resists moisture andsunlight exposure. For indoor cables, the outer jacket 52 may be aflame-retardant jacket that can be color-coded to identify the fibers 60a, 60 b inside the cable assembly 10, e.g., PVC, LSZH, TPU, ETFE orOFNP. The outer jacket 52 thickness can be approximately 0.25 mm-5 mmand come in a variety of colors, e.g., yellow, orange, aqua, blue, etc.

Under the outer jacket 52 is the outer pull material 56. The outer pullmaterial 56 can be aramid fibers and a water blocking material, e.g.,yarn. The outer pull material 56 can absorb the tension needed to pullthe cable assembly 50 during installation. Aramid fibers are usedbecause of their strength and the fact that they do not stretch. Ifpulled hard, the aramid fibers will not stretch but may eventually breakwhen tension exceeds their limits. For short term stresses, the maximumtension is approximately 800N. For long term stresses, the maximumtension is approximately 600N.

In between the outer jacket 52 and the pull material 56 is the one ormore push bodies 54 a, 54 b. The push bodies 54 a, 54 b can be one ormore rigid wires. The push bodies 54 a, 54 b is capable of acting as afish tape but can be bent to accommodate tight turns. The push bodies 54a, 54 b can have a diameter of 0.2 to 0.6 mm. The push bodies 54 a, 54 bcan be made steel. In some implementations, the push bodies 54 a, 54 bcan be partially attached to an inside wall of the outer layer.

The armor 58 can be a non-interlocking stainless steel tube, e.g. SUS204. The benefit of using a non-interlocking armor is that the bendradius is substantially smaller than a bend radius of an interlockedsteel tube. It is also much lighter and easier to work with. The armor58 can be a spiral tube having a gap 59 between each spiraling ring, thegap 59 can be 0.05 mm to 1 mm. The armor 16 cab be a spiral tube havingan OD of approximately 1.5 mm-5.5 mm, a thickness of approximately 0.25mm-0.75 mm and an inner diameter of approximately 0.75 mm-5.25 mm. Thearmor has a crush resistance of approximately ≥100 KGf/100 mm. The armor58 offers increased crush protection, higher axial strength andcorrosion resistance. However, other armored steel tubes arecontemplated.

Optical fibers 22 a. 22 b consist of a core and a cladding layer,selected for total internal reflection due to the difference in therefractive index between the two. In practical fibers, the cladding isusually coated with a layer of acrylate polymer or polyimide. Thiscoating protects the fiber from damage but does not contribute to itsoptical waveguide properties. Individual coated fibers (or fibers formedinto ribbons or bundles) then have a tough resin buffer layer and/orcore tube(s) extruded around them to form the cable core. A standardfiber has a primary buffer coating of approximately 250 microns and canadd a tight buffer coating such as a soft protective coating applieddirectly to the 250 micron coated fiber to provide additional protectionfor the fiber, allowing easier handling and even direct termination forthe fiber.

In some implementations, the optical fibers 20 can be 62.5/125 μmmultimode fibers, 50/125 μm 10G OM3/OM4 fibers, 9/125 μm single modeG.652.D fibers, 9/125 μm single mode bend-insensitive fibers, or anysuitable fibers, for example, G.657.A1, G.657.A2, G.657.B1, G.657.B2,G.657.B3.

The fiber optic cable assembly 50 can have (1) a short term minimumallowable tension strength of 150N and a long term minimum allowabletension strength of 80N, (2) a short term crush load (N/100m) of 2500Nand a long term crush load (N/100m) of 1000N, (3) an insertion loss(attenuation) of 1310 nm-1550 nm and (4) a minimum bend radius of 20 fordynamic and 10D for static.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of thedisclosed technology or of what can be claimed, but rather asdescriptions of features specific to particular implementations of thedisclosed technology. Certain features that are described in thisspecification in the context of separate implementations can also beimplemented in combination in a single implementation. Conversely,various features that are described in the context of a singleimplementation can also be implemented in multiple implementationsseparately or in any suitable subcombination. Moreover, althoughfeatures can be described above as acting in certain combinations andeven initially claimed as such, one or more features from a claimedcombination can in some cases be excised from the combination, and theclaimed combination can be directed to a subcombination or variation ofa subcombination.

The foregoing Detailed Description is to be understood as being in everyrespect illustrative, but not restrictive, and the scope of thedisclosed technology disclosed herein is not to be determined from theDetailed Description, but rather from the claims as interpretedaccording to the full breadth permitted by the patent laws. It is to beunderstood that the implementations shown and described herein are onlyillustrative of the principles of the disclosed technology and thatvarious modifications can be implemented without departing from thescope and spirit of the disclosed technology.

The invention claimed is:
 1. A fiber optic cable assembly comprising: anouter jacket, the outer jacket being made from polyethylene; a pullmaterial, the pull material being made from aramid and water blockingfibers; a push body, the push body being made from a rigid material sothat the fiber optic cable assembly can be pushed during installation;and at least one fiber optic fiber.
 2. The fiber optic cable assembly ofclaim 1 wherein the push body is at least one rigid wire.
 3. The fiberoptic cable assembly of claim 2 wherein the at least one rigid wire ismade from steel.
 4. The fiber optic cable assembly of claim 3 whereinthe at least one rigid wire has a diameter of 0.2 to 0.6 mm.
 5. Thefiber optic cable assembly of claim 2 further comprising: an armor body.6. The fiber optic cable assembly of claim 5 wherein the armor body issteel micro armor.
 7. The fiber optic cable assembly of claim 5 whereinthe pull material is sandwiched between the outer layer and the armorbody.
 8. The fiber optic cable assembly of claim 2 wherein the at leastone rigid wire is partially attached to an inside wall of the outerlayer.
 9. The fiber optic cable assembly of claim 1 wherein the at leastone fiber optic fiber is a tight buffer fiber.
 10. The fiber optic cableassembly of claim 1 wherein the push body is a rigid, hollow tube. 11.The fiber optic cable assembly of claim 10 wherein the tube is seamless.12. The fiber optic cable assembly of claim 11 wherein the tube is madefrom stainless steel.
 13. The fiber optic cable assembly of claim 12wherein the tube is made from SUS
 304. 14. The fiber optic cableassembly of claim 10 wherein the tube has an outer diameter of 0.8 to2.2 mm.
 15. The fiber optic cable assembly of claim 10 wherein the tubehas an inner diameter of 0.6 to 1.2 mm.
 16. The fiber optic cableassembly of claim 10 wherein the tube has thickness of 0.1 to 0.3 mm.17. The fiber optic cable assembly of claim 10 further comprising: anarmor body.
 18. The fiber optic cable assembly of claim 17 wherein thearmor body is steel tube.
 19. The fiber optic cable assembly of claim 10further comprising: a strengthening material surrounding the at leastone fiber optic fiber underneath the push body.
 20. The fiber opticcable assembly of claim 19 wherein the strengthening material is madefrom aramid and water blocking fibers.
 21. The fiber optic cableassembly of claim 10 wherein the pull material is made from aramid andwater blocking fibers.
 22. The fiber optic cable assembly of claim 21wherein the pull material is sandwiched between the outer layer and thearmor body.